Selected medicinal plants having repellent activity were tested against the larval stages and adults of mosquitoes, namely, Aedes aegypti Linn. and Culex quinquefasciatus Say. Ethanol crude extracts of the stems, branches, leaves, flowers, fruits and roots of Cymbopogon nardus Rendle, Citrus hystrix DC., Chrysanthemum indicum Linn., Azadirachta indica var. siamensis Valeton, Ocimum sanctum Linn., Alpinia galanga Swaztz and Acorus calamus Linn. containing various components of repellent substances were used. The single and mixed solutions of two species of plant crude extracts were mixed with olive oil and musk in the ratio of 20: 2: 0.1, respectively. The 0.5 ml of the mixed repellent solutions were applied on the ventral forearms of some volunteers to assess potential repellent efficacy and duration. The results indicated that the single solution of C. nardus extract and the mixed solution of C. nardus and C. indicum extract showed repellent activities for 120 minutes. These extracts also showed larvicidal activities against the afore-mentioned mosquitoes.